/proc/meminfo – This file reports statistics about memory usage on the system. It is used by free to report the amount of free and used memory (both physical and swap) on the system as well as the shared memory and buffers used by the kernel. You can also use free, vmstat and other tools to find out the same information.

I needed to filter access by IP using varnish acl, but when your varnish is behind a Amazon ELB Load Balancer, by default it doesn’t work, so here is the solution! Tested using Linux Amazon Linux AMI release 2015.03